You need to say where you are, roughly.

Post photos from further back so we can see the whole area around the trees.

Are the trees planted correctly (not too high or too low in the ground)?

What is your soil type?

How are you watering the trees - via drip, etc.?

Newly planted firs need a lot of water regularly in the first year (being careful not to overwater) especially as summer temps/sun ramp up. How are you determining that the trees are receiving enough water? Have you (carefully) dug down a few inches around the root ball to check soil moisture? Is the soil dry or is there pooled water?

I am in zone 5A, Minneapolis area

That amount of loss isn't significant yet and may just be the result of it being dug out and burlapped. Me, I would have removed the burlap after placed in the hole......

Many times, a b&b tree will have a root ball that's clay soil.

You need to take a tablespoon or the like and dig into the original root ball and see if it's clay and see if it's dry inside.

A clay root ball is difficult to soak up again once it's dried out, so you may need to put a garden hose, at a trickle, next to the trunk, and let it run all day or all night, just to get that clay ball soaked up thoroughly again.

Those short lower branches will never get enough sun to grow out to the same distance as the upper branches. You can just cut them off.

The longer branches a little higher will grow out and eventually hide the lower 6" to a foot of the bottom trunk, so it won't be noticeable in a few years.

I'd follow Bill's advice. B&B stock is almost always grown in clay to protect what remains of the rootball. Depending on how the tree was held by the nursery or landscaper and for how long, it could very easily have dried out. This is the most frequent cause of B&B failures. I always suggest soaking the rootball in a large bucket to rehydrate thoroughly before planting.

Not to ask something obvious, but have you inspected those branches for damage? The lower branches of evergreens can get easily roughed up when the trees are dug with a tree spade for balled & burlap sale - especially if they weren't tied up with a mechanical tree tier before digging. Or the landscapers could have broken branches in transport and installation. Partially broken evergreen branches can sometimes take many, many weeks to fully dry out and turn brown.

Also, I wouldn't assume that tree has a clay ball under it. Of the largest nurseries that I have had contact with in Minnesota, the majority are not growing in heavy clay. Certainly not the ones that mass produce evergreens. However, if the tree was purchased from Bachman's or Gerten's wholesale yard, I wouldn't be surprised if they brought trees in from Illinois or Wisconsin that could be in clay.

Regardless of the tree ball soil type, I'd be skeptical of any excessive drying out of that tree ball. Most of the Twin Cities and surrounding area has had around 8" to 10" of rain in June alone. You shouldn't have had to water that tree once if you've been getting a weekly heavy soaking (or two.) As Design Fan posted, dig down next to the tree ball and check your soil if you are ever unsure of how dry or wet things are beneath the surface.

A 6' balled & burlap balsam fir probably has a 26" to 28" ball under it that weighs over 400 pounds. That root ball isn't fitting in a bucket.

The B&B's I have planted myself have always been giant clay balls. I have always gently freed as much root mass as I can from the clay, gotten rid of all teh broken-off clay, and then planted the tree into a hole with native soil. It's worth the effort to do this, especially if your native soil doesn't tend toward clay.

So the question for you is -- did the landscaper plant it properly? Did they remove the wire caging and burlap before planting? Was the root ball thoroughly moist at planting time? (dry clay = brick).

If the rootball is too large or heavy to soak in a bucket or wheelbarrow, make sure it is still well hydrated before planting......it is very difficult to rehydrate the rootball after planting. The existing soil will soak up whatever moisture is available, leaving the rootball remaining dry.

And it may be different with different vendors but most nurseries here (west coast) will invalidate their guarantee if the B&B rootball is disturbed. Disturbing or removing portions of the clay pull off what fine feeder roots are available, stressing an already heavily stressed plant and reducing its ability to establish well. Possibly even killing it.

And never, NEVER rely just on rainfall to irrigate a newly planted tree, especially in summer!